1. Field of the Invention
The present invention relates to an apparatus for manufacturing an optical information recording medium such as a disk for use in recording of digital data, and from which recorded information is read by using a laser beam. Such a recording medium is used in, for example, audio and video systems and in data recording of an information equipment.
2. Description of the Related Art
A method disclosed in Japanese Patent Disclosure (Kokai) No. 62-187004 is known as a means for manufacturing an optical disk. In this manufacturing method, a resin which cures upon radiation of ultraviolet rays thereon is sandwiched between a stamper having on its surface undulations for expressing data, and serving as a master and a disk substrate composed of a synthetic resin. Radiation of ultraviolet rays onto the layer of ultraviolet-curing resin, now having the undulated surface of the stamper imprinted thereon, causes the resin layer to be formed integral with the surface of the disk substrate. Thereafter, the resin layer and the stamper are separated, leaving a disk having an optical information recording surface formed thereon.
In order to manufacture an optical disk as described above, the ultraviolet-curing resin layer located between the disk substrate and the stamper must be formed having a uniform thickness. Exemplary methods of forming this resin layer are those disclosed in Japanese Patent Disclosure (Kokai) Nos. 53-116105 and 58-173623. However, using even these methods, bubbles are sometimes formed in the resin layer. Consequently, it is difficult, using conventional methods, to manufacture, on a consistent basis, optical disks with high precision through preventing formation of bubbles.
In addition, the resin layer on which the data recorded on the surface of the stamper is imprinted, upon radiation thereon of ultraviolet rays, must subsequently be separated from the stamper. Japanese Patent Disclosure (Kokai) No. 62-187004, for example, teaches a method wherein a push-up member located at a central portion of the disk substrate is pushed upward by a pin operated by air pressure, thereby to separate the resin layer from the stamper surface.
However, when such a mechanical force is used to separate the resin layer from the stamper, it creates a strong flexing force which acts not only on the disk substrate but also on the resin layer on which the recorded data has been imprinted, thereby damaging that surface of the resin layer. Further, the flexing force may cause distortion of, the disk substrate which supports the resin layer, and, when the disk substrate is pushed upward, the stamper may become separated from its support table and be pushed upward together with the disk substrate, i.e. resulting in non-separation of these two elements.
In consideration of the above problems, a method of fixing the stamper to the table has been proposed in Japanese Patent Disclosure (Kokai) No. 60-47253. According to this method, a first electromagnet is located at a position corresponding to a central portion of the stamper, and a second ring-like electromagnet is set to correspond to the periphery of the stamper, thereby attracting and holding the stamper consisting of a magnetic material. To separate the resin layer from the stamper, the first electromagnet is switched off, with the periphery of the stamper remaining attracted to the second electromagnet. In this state, by moving the stamper away from the resin layer, the resin is separated sequentially from the periphery of the stamper. However, this separating method requires a complicated arrangement of first and second electromagnets set in correspondence with the shape of the stamper. In addition, a complicated on/off control must be performed in respect of the two electromagnets, and an undesirably strong force acts on the resin layer during its separation from the stamper.